Method and system for adaptive modification of cell boundary

ABSTRACT

A method and system for reducing interference in a cellular radio communications network. At least one parameter affecting user terminals within a cell is adjusted such that the cell boundary is modified, such that interference in the network is reduced. In alternative embodiments the at least one parameter is adjusted adaptively.

FIELD

Embodiments of the invention relate generally to cellular radiocommunication systems, and more particularly to the modification ofindividual cell topography in cellular radio communication systems tofacilitate increased downlink capacity requirements.

BACKGROUND

The trend toward increased downlink capacity requirements in cellularradio communications systems is continuing with the expanding menu ofhigh data rate services. Typical network planning strategies forcellular radio communication networks present drawbacks in regard touser handoff and system load balancing for an interference-limited,high-data-rate environment.

Cellular radio communication systems (hereafter “communication systems”)are typically comprised of a number of cells, with each cellcorresponding roughly to a geographical area. Each cell has anassociated base station (BS) which is a local central cite providingaccess to the communication system to a number of radiotransmitter/receiver units (user terminals (UTs)) within the cell. A BSincludes at least one antenna and a transceiver system providing radioservice within the cell. A base station of a typical communicationsystem may have three antennas, oriented 120 degrees apart, definingthree cells (also referred to as sectors_([GDC1])). The BSs couple tobase station controllers (BSCs) with each BSC serving a plurality ofBSs. The BSCs also couple to a mobile switching center (MSC) which mayinterface other MCSs and the Public Switched Telephone Network (PSTN).Together, the BSs, BSCs and the MSCs form a cellular radio communicationsystem or network_([GDC2]). Network planners typically consider manyfactors in determining network features such as location of the BSs, BStransmission power (e.g., pilot power) as well as BS antenna physicalcharacteristics (e.g., antenna downtilt). The factors considered mayinclude population demographics, geographical formations, and UT usepatterns, among others. Typically such network features remain staticand cannot be adjusted to suit dynamic network requirements.

In typical radio cellular communications systems the BS communicateswith each UT using a separate temporary radio channel. A channel is aset of two connections, the downlink, for transmitting to the UT and theuplink, for receiving from the UT. Due to the limited number of radiochannel frequencies available to support such networks, the efficientuse and reuse of available channels is critical to increasing networkcapacity. Frequency reuse is based on the concept of assigning adistinct group of channels to each neighboring cell, and then assigningthe same group of channels to cells that are far enough away from eachother so that their use of the same frequencies does not result insubstantial interference. The number of cells that are assigned distinctchannel groups determines the frequency reuse factor.

Some communication systems employ a low frequency reuse factor. Forexample, code division multiple access (CDMA) systems includingcdma2000, wideband CDMA (W-CDMA), and IS95, and high data rate (HDR), aswell as enhanced data GSM environment (EDGE), employ a frequency reusefactor of 1. That is, CDMA systems employ a direct sequence spreadspectrum technology in which all of the available frequencies are usedin each cell. Each UT within a cell is assigned a distinct orthogonalspreading code that uniquely identifies the UT and is used to decodetransmissions from the BS. This technology increases the number of UTsthat can be served by a BS by permitting all UTs within a cell totransmit simultaneously in the allocated frequency band. However, sinceeach cell is using the entire frequency band, disjoint groups of channelfrequencies are not available for use in neighboring cells. Using theentire frequency band can lead to mutual interference by proximate UTslocated in different cells as described below.

In a typical communication system, each BS may serve an area comprisedof multiple cells with the shape of each cell defined by the antennapattern of one or more BS antennas. The size of each cell is determinedby the pilot signal strength (pilot power) transmitted from the BS. Thepilot signal is an unmodulated, direct-sequence spread spectrum signal,transmitted continuously by each BS, for each cell, which allows each UTto acquire the timing of the downlink channel. When a UT becomesoperational, it measures the pilot power of the surrounding BSs. The UTestablishes communication with the BS having the strongest pilot power.

Mutual Interference Between User Terminals

UTs in a CDMA system located within the same cell typically do notexhibit significant mutual interference due to the fact that each UT isassigned a mutually orthogonal downlink transmission code (code).Therefore, for UTs within a cell, the interference (other than noise andimplementation effects) is virtually zero (if the multi-path spread isnot too large). For such UTs, high-data-rate downlink transmissions arepossible_([GDC3]). This is because, in the CDMA system, total chiptransmission rate remains constant, therefore, if a higher data rate isrequired the spreading factor of the codes must be reduced_([GDC4]). Thespreading factor of the codes is directly related to the amount ofinterference through which communication signals may be discerned. So,for UTs exhibiting little mutual interference the spreading factor maybe reduced substantially thereby allowing a proportionally higherdownlink data transmission rate. However, because each cell uses adifferent scrambling code set, the codes assigned to UTs of differentcells are not guaranteed mutual orthogonality. Therefore, ahigh-data-rate transmission to such UTs may require a spreading factorreduced to such a degree that the communication signal cannot bediscerned in the presence of mutual interference. In such case, a UTexperiencing interference from a neighboring cell will request morepower in order to maintain a signal-to-interference-plus-noise ratio(SINR) required, for example, by the quality of service (QoS) specified.The increased power to one UT increases the interference to theproximate UT of the neighboring cell. Eventually, some UTs get droppedand capacity is reduced. Therefore, proximate UTs located in differentcells may not be capable of high-data-rate downlink transmissions due tomutual interference. Reducing this mutual interference between UTs isbecoming more imperative as the trend toward greater downlink capacityrequirements continues.

Load Balancing

Load balancing can also cause mutual interference in a high downlinkdata transmission rate environment. The number of simultaneous, activeusers (capacity) served within a particular cell may be limited by BSthroughput or number of available codes. Thus, the number of users thatmay be supported by each cell is limited. For this reason it isdesirable to distribute the number of active UTs as evenly as possibleamong the available cells (i.e., balance the load). There are a numberof ways to effect load balancing. One such method involves adjusting thepilot power of one or more cells to change the size of the cell therebyencompassing more, or less, UTs to be served through a particular cell.

Moreover, because the codes assigned to each UT for uplink transmissionsare not orthogonal as they are for the downlink transmissions, abalanced load is effective when the performance of the system is limitedby BS throughput or number of UTs that can be served (uplink limitedenvironment). However, if the limiting factor is interference betweenUTs, then a balanced load may actually exacerbate the problem. This isbecause inter-cell code orthogonality is not provided, and loadbalancing may cause several proximate UTs to be served by differentcells having non-orthogonal spreading codes, thus increasing mutualinterference. Such mutual interference is particularly problematic in ahigh-data-rate downlink environment. That is, because each of two,proximate, high-data-rate UTs having non-orthogonal codes may producethe effective equivalent mutual interference of a large group of typicalUTs having non-orthogonal codes, the likelihood of such mutualinterference causing degradation of system performance is increased in ahigh-data-rate environment.

Soft Handover

Another aspect of typical CDMA cellular radio communications systemsthat may degrade system performance through intercell interference in ahigh downlink data rate environment is that of “soft handover”. If a UTis at a cell border, the power is limited and the channel is weak. Softhandover is a way to compensate for the poor quality by serving the UTthrough two or more cells, this corresponds to UTs being in a regionwhere two or more cell boundaries overlap. The UT generates ameasurement report that includes the pilot power of each cell throughwhich the UT is being served (active set) as well as the pilot power ofthe neighboring cells (neighboring set). This information is used todetermine when the UT should be placed in, or taken out, of softhandover. The measurement report may include various performancemeasurements in addition to pilot power (e.g. a pilotpower-to-interference ratio). This information is reported to the BSCs.Where the UT is being served through cells provided by BSs that arecoupled to different BSCs, the measurement report may be forwarded tothe MSC.

Soft handover works well for uplink transmissions, though for downlinktransmissions, much of the gain of soft handover is lost. This isbecause soft handover provides large gains when the UT receives equalpower through each of the two cells, but it is difficult to aligntransmission power so that the UT receives equal power through each ofthe two cells. Moreover if one of the channels is not fading, then softhandover is not necessary anyway. In the downlink, the interference dueto being served through two or more cells using non-orthogonal codes mayvitiate the benefits of soft handover.

SUMMARY

Embodiments of the invention provide a method and system for reducinginterference in a cellular radio communications network. One or moreparameters affecting user terminals within a cell is adjusted such thatthe cell boundary is modified, thereby redistributing a cell load suchthat interference in the network is reduced. In one embodiment the oneor more parameters is adjusted adaptively.

Other features and advantages of embodiments of the invention will beapparent from the accompanying drawings and from the detaileddescription, which follow below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be best understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 is a process flow diagram of a method for adjusting parameters toaffect system performance in accordance with one embodiment of theinvention;

FIG. 2 illustrates an exemplary cellular radio communications networkproviding parameter adjustment functionality in accordance with anembodiment of the invention;

FIG. 3A shows the portion of network 200 containing BSs 210 and 216;

FIG. 3B shows the portion of network 200 containing BS 210;

FIG. 3C shows the portion of network 200 containing BS 210 andillustrates the result of adjusting a different antenna parameter inorder to eliminate inter-cell interference between UTs 3 and 4;

FIG. 4 illustrates application of the invention to effect load balancingin accordance with one embodiment;

FIG. 5 illustrates application of the invention to remove UTs from softhandover in accordance with one embodiment; and

FIG. 6 is process flow diagram of an exemplary algorithm to determinewhich cell will include the UTs in soft handover.

DETAILED DESCRIPTION

Overview

An embodiment of the invention provides a method and system for reducinginterference in a cellular radio communications network. At least oneparameter affecting user terminals is adjusted such that the celltopography (i.e., size and shape, or boundary) is modified, therebyredistributing a cell load such that interference in the network isreduced. This allows use of the network by, for example, two proximatehigh-data-rate users that otherwise may have been dropped from thenetwork due to mutual inter-cell interference in prior art communicationsystems. In one embodiment, at least one parameter is adjustedadaptively, that is, in response to changing network conditions. Inanother embodiment the pilot power and an antenna parameter are adjustedto increase network capacity and/or cell coverage. In such an embodimentnetwork capacity may be increased through load balancing. One advantageof such an embodiment is to provide more intricate, and therefore moreeffective, load balancing. In still another embodiment, network plannersmay consider adaptive parameters when determining static networkparameters, which will allow for more efficient network planning.

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knownstructures and techniques have not been shown in detail. Referencethroughout the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. Thus, the appearance of the phrases “in oneembodiment” or “in an embodiment” in various places throughout thespecification are not necessarily all referring to the same embodiment.Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments.

Similarly, it should be appreciated that in the foregoing description ofexemplary embodiments of the invention, various features of theinvention are sometimes grouped together in a single embodiment, figure,or description thereof for the purpose of streamlining the disclosureand aiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claimed invention requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the Detailed Description are hereby expressly incorporatedinto this Detailed Description, with each claim standing on its own as aseparate embodiment of this invention.

FIG. 1 is a process flow diagram in accordance with one embodiment ofthe invention. Process 100 shown in FIG. 1 begins at operation 105 inwhich a controller device, which may be the BS, BSC or MSC, obtains aperformance indicator (e.g., performance measurement) associated withone or more user terminals. For example, consider two high-data-rate UTseach being served through a different cell (i.e., each has anon-orthogonal spreading code). Because each UT is requesting ahigh-data-rate, its spreading code factor will be proportionatelyreduced. This results in a high level of mutual interference, which inturn leads to requests from each UT, to their respective BSs, toincrease transmission power. The requests for increased transmissionpower, or the pilot power-to-interference ratio included in themeasurement report from the UTs may be used as an indicator of mutualinter-cell interference. In one embodiment, the performance indicatorindicates whether a UT is in soft handover.

At operation 110, the controller device determines a parameter foraffecting the cell boundary (size and/or shape) of the cells in anappropriate way. For example, in the case of two high-data-rate UTsexhibiting mutual interference, a parameter may be determined thataffects the cell boundary in such a way that adjustment of the parameterwill modify the boundary of one or both of the cells such that themutually interfering UTs will both be included in one cell and excludedfrom the other. In another embodiment, this parameter may be pilotpower, various antenna characteristic parameters, or combinationsthereof.

At operation 115, the controller device determines the amount by whichthe determined parameter is to be adjusted, for example, based upon theperformance measurement_([GDC5]). The controller device then adjusts theparameter accordingly. The parameter may be adjusted adaptively in oneembodiment. For example, if the two high-data-rate UTs exhibiting mutualinterference are both in use in the network over a particular period oftime, the parameter may be adjusted at such time and restored to itsoriginal value when the two high-data-rate UTs are no longer present inthe network.

At operation 120 the process is repeated if the desired systemperformance is not obtained by the parameter adjustment of operation115.

FIG. 2 illustrates an example cellular radio communications networkproviding parameter adjustment functionality in accordance with anembodiment of the invention. Network 200 includes MSC 202. Coupled toMSC 202 are BSCs 204, 205, and 206. BSC 204 has BSs 208 and 210 coupledto it, BSC 205 has BSs 212 and 214 coupled to it, and BSC 20 has BS 216coupled to it. In accordance with an embodiment of the invention, theMSC 202, and each BSC, 204, 205, and 206, contain parameter adjustmentfunctionality, labeled 221–224, respectively, which may includesoftware, hardware, or a combination thereof. Alternatively, oradditionally, each BS may contain such functionality. Each BS, 208, 210,212, 214, and 216, serves an area comprised of three cells, labeled A,B, and C, for each BS. Network 200 also includes a number of UTs, 1–20,positioned to illustrate various embodiments of the invention.

UTs 1 and 2, located in cells 210C and 216A respectively, arehigh-data-rate UTs. Since UTs 1 and 2 are in different cells, they areassigned non-orthogonal spreading codes. Because they are high-data-rateUTs, they have a reduced spreading factor. This means that UTs 1 and 2may exhibit high mutual inter-cell interference. The same situationapplies to UTs 3 and 4 located in cells 210A and 210C respectively.

Cell 214A, through which seven UTs, UTs 8–14 are served, illustrates anoverloaded cell (e.g., cell capacity is five UTs). Cell 214A may beoverloaded due to the limit on the number of codes that can be assignedwithin the cell, or may be overloaded due to total cell throughput. Inthe latter instance, fewer high-data-rate UTs may effectively replacemultiple typical data rate (e.g., voice) UTs in regard to overloadingthe cell. Nearby cells, 212C and 216B serve UTs 15–17 and 5–7,respectively and are not loaded to capacity.

UTs 18 and 19, located at the border of cells 208C and 212A, arehigh-data-rate UTs that are in soft handover region 25 and both arebeing served through cells 208C and 212A by BSs 208 and 212. UT 20,located at the border of cells 208C, 210B, and 212A, is also in softhandover region 25 and is being served through cells 208C, 210B, and212A by BSs 208, 210, and 212. As described above, because for downlinktransmission capacity requirements are often much higher, soft handovermay not be desirable. That is, soft handover gain is vitiated by themutual inter-cell interference caused by the UTs having non-orthogonalspreading codes (and due to the fact that it is difficult to equalizethe power received from each of the two or more BSs serving the UTs).

Exemplary Applications

The following portion of the description will briefly describe howvarious embodiments of the invention may be applied to the performancedegrading state of network 200.

Inter-Cell Interference

FIGS. 3A, 3B, and 3C illustrate application of the invention to reduceinter-cell interference in accordance with various embodiments.

FIG. 3A shows the portion of network 200 containing BSs 210 and 216. Thecell boundary of cell 210C has been modified (extended) to encompassboth UT 1 and UT 2, and the boundary of cell 216A been modified(retracted) to exclude UT 2, thereby eliminating inter-cellinterference. That is, because UT 1 and UT 2 are now being servedthrough the same cell, they are now assigned mutually orthogonalspreading codes. In one embodiment, this cell boundary modification isaccomplished by an increase in pilot power for cell 210C and acorresponding reduction in pilot power of cell 216A. The determinationof which cell boundary to extend and which to retract is made by randomselection or based on consideration of various network conditions.

Because BSs 210 and 216 are coupled to different BSCs, namely BSCs 204and 206, the operations of receiving the performance indicator, anddetermining and adjusting the appropriate parameter(s) of each cell areaccomplished at the MSC 102. In an alternative embodiment, suchoperations are accomplished at the relevant BSC in conjunction with theMSC.

Because cell 210C now contains several high-data-rate UTs, UTs 1–3,while cell 216A now contains none, the load, with respect to the twocells, is unbalanced. However, as long as cell 210C is not overloaded(i.e., has not exceeded throughput or code capacity), the benefit ofreduced inter-cell interference may outweigh the detriment of anunbalanced load.

FIG. 3B shows the portion of network 200 containing BS 210. The cellboundary of cell 210C has been shifted to encompass both UT 3 and UT 4,and the boundary of cell 210A has likewise been shifted to exclude UT 4,thereby eliminating intercell interference. Note that, in this caseadjusting pilot power would not result in inclusion of both of themutually interfering UTs in a single cell (other than by eliminatingpilot power completely for cell 210A). Therefore a parameter other thanpilot power is determined, in one embodiment, as described in referenceto operation 110 of FIG. 1. For example, the illustrated shift in cellboundary is accomplished by appropriately adjusting the antenna azimuth(direction) of the BS antenna(s) that define(s) each cell. Because cells210A and 210C are provided by the same BS, namely BS 210, the operationsof receiving the performance indicator, and determining and adjustingthe appropriate parameter(s) of each cell are accomplished at BSC 204 orMSC 102. In an alternative embodiment, such operations are accomplishedat the relevant BS (e.g., BS 210).

FIG. 3C shows the portion of network 200 containing BS 210 andillustrates the result of adjusting a different antenna parameter inorder to eliminate inter-cell interference between UTs 3 and 4. That is,it may not be desirable to shift the cell boundary. In this case, thecell boundary of cell 210C has been modified to encompass both UT 3 andUT 4, and the boundary of cell 210A has likewise been modified toexclude UT 4, thereby eliminating inter-cell interference. In oneembodiment, such modification is accomplished by appropriately adjustingthe antenna pattern of each cell. For example, if each sector is definedby multiple antennas, the phase shift of each antenna is electronicallyadjusted to alter the antenna pattern, thus modifying the cell boundary.

Load Balancing

FIG. 4 illustrates application of the invention to effect load balancingin accordance with one embodiment. FIG. 4 shows the portion of network200 containing BSs 212, 214, and 216. The cell boundary of cell 216B hasbeen modified such that cell 216B now encompasses UTs 6 and 7 as well asUTs 3–5 for a total of five UTs. The cell boundary of cell 214A has beenmodified, correspondingly such that cell 216A now excludes UTs 6 and 7and includes only five UTs, namely UTs 8–12. Therefore, cell 214A is nolonger overloaded and load balancing has been efficiently effected. Themodification of the cell boundary for cells 214A and 216B may beaccomplished by adjusting the pilot power and one or more antennaparameters of each cell (e.g., antenna pattern). That is, variousantenna parameters may be adjusted in conjunction with adjusting pilotpower depending on the desired modification of the cells' boundaries.Note that had the pilot power of cells 214A and 216B, alone, beenmodified (decreased and increased, respectively), the resultant cellboundary of cell 216B may have encompassed UTs 13–15 thereby overloadingcell 216B. To avoid this, the pilot power of cell 212C may have to beadjusted.

Soft Handover

FIG. 5 illustrates application of the invention to remove UTs from softhandover in accordance with one embodiment. FIG. 5 shows the portion ofnetwork 200 containing BSs 208, 210, and 212. The cell boundary of cell212A has been modified such that cell 212A now encompasses UTs 18, 19and 20, which were in soft handover. The cell boundary of cell 212A hasbeen modified by adjusting pilot power, one or more antenna parameters,or a combination of pilot power and antenna parameters. In oneembodiment, removing UTs 18, 19, and 20 from soft handover involvesmodification of the cell boundaries of cells 208C and 210B through theadjustment of one or more parameters (e.g., reduction of pilot power),as shown.

Because BSs 208, 210, and 212 are coupled to different BSCs, namely BSCs204 and 205, the operations of receiving the performance indicator, anddetermining and adjusting the appropriate parameter(s) of each cell maybe accomplished at the MSC 102.

As discussed above in reference to FIG. 3C, the determination of whichcell boundary to modify such that the cell includes the UTs in the softhandover region is made by random selection for one embodiment. In analternative embodiment, the determination of which cell boundary tomodify is based on consideration of various network conditions.

FIG. 6 is process flow diagram of an exemplary algorithm to determinewhich cell will include the UTs in soft handover.

Process 600 begins with operation 605 in which soft handover regions areidentified. In one embodiment of the invention, this is done by analysisof the measurement report sent to the BSs by each UT. The measurementreport identifies the cells (two or more for a UT in soft handover) thatthe UT is communicating through. These cells are known as the activeset. The measurement report also includes the pilot power for each cellof the active set as well as other information.

At operation 610 a determination is made as to whether the cells areproviding equal resources to UTs in the soft handover region. In oneembodiment, a determination of resources provided is the number of UTs acell is serving, the total cell throughput, or a function of total UTthroughput and total UT transmission power. For example, referring againto FIG. 2, cell 210B is serving only one UT (UT 20).

At operation 615, if the provided resources are not equal, then adetermination is made as to which cell is providing the least resources.This is done by examining the active sets of the UTs in soft handover,for example, where the resource is the number of UTs being served.

At operation 620 at least one parameter of those cells providing theleast resources is adjusted to modify the cell boundary to exclude theUTs in the soft handover region. For example, referring again to FIG. 2,since cell 210B serves only one UT in soft handover (UT 20), the pilotpower of cell 210B is reduced such that UTs in the soft handover regionare excluded from cell 210B (as shown in FIG. 5).

At operation 625, if the resources provided by each cell are equal, thena random selection is made between the cells. One or more parameters ofone or more cells is adjusted to modify the cell boundaries so that theUTs in soft handover are included within only one cell, such that theUTs are no longer in a soft handover region, and are excluded from theother cell(s). With the boundaries shifted, interference drops, andtherefore may allow a reduction in total transmitted pilot power.

General Matters

Embodiments of the invention may be applied to reduce inter-cellinterference, to provide more efficient load-balancing, and to avoid thedrawbacks of soft handover. While several embodiments have beendescribed in relation to their application in a high downlink data rateenvironment, embodiments of the invention may be likewise applicable totypical data rate (voice) environments and uplink environments. Manyother applications are possible as well, such as the determination ofvarious network parameters based upon the ability to adaptively adjustother parameters, during network planning.

The invention includes various operations. It will be apparent to thoseskilled in the art that the operations of the invention may be performedby hardware components or may be embodied in machine-executableinstructions, which may be used to cause a general-purpose orspecial-purpose processor or logic circuits programmed with theinstructions to perform the operations. Alternatively, the steps may beperformed by a combination of hardware and software. The invention maybe provided as a computer program product that may include amachine-readable medium having stored thereon instructions, which may beused to program a computer (or other electronic devices) to perform aprocess according to the invention. The machine-readable medium mayinclude, but is not limited to, floppy diskettes, optical disks,CD-ROMs, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetor optical cards, flash memory, or other type of media/machine-readablemedium suitable for storing electronic instructions. Moreover, theinvention may also be downloaded as a computer program product, whereinthe program may be transferred from a remote computer to a requestingcomputer by way of data signals embodied in a carrier wave or otherpropagation medium via a communication cell (e.g., a modem or networkconnection). The operations may be performed at a BS, a BSC, a MSC, orperformed by a combination of these control devices.

Embodiments have been herein described in reference to a CDMA system,but the invention is not limited to such systems or even to systemsemploying a low frequency reuse factor. Importantly, while the inventionhas been described in the context of a cellular radio communicationsystem, it can be applied to a wide variety of different systems inwhich data are exchanged. Such systems include voice, video, music,broadcast and other types of data systems without external connections.Many of the methods are described in their most basic form butoperations can be added to or deleted from any of the methods withoutdeparting from the basic scope of the invention.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, but can be practiced withmodification and alteration within the spirit and scope of the appendedclaims. The description is thus to be regarded as illustrative insteadof limiting.

1. A method for reducing inter-cell interference in a cellular radiocommunications network comprising: receiving an indication of anincrease in an inter-cell interference between a first user terminal,being served by a first cell, and a second user terminal, being servedby a second cell; and adaptively adjusting a pilot power of one or bothof the first cell and the second cell to modify a cell boundary of oneor both of the first cell and the second cell in response to saidindication by: modifying the cell boundary such that the first andsecond user terminals are served by the same one of said first andsecond cells.
 2. The method of claim 1, wherein adaptively adjusting apilot power of one or both of the first cell and the second cellincludes increasing the pilot power of the first cell and decreasing thepilot power of the second cell.
 3. The method of claim 2, whereinadjusting the pilot power of one or both of the first cell and thesecond cell further comprises adjusting said pilot power to unbalance acell load of the first cell and a cell load of the second cell withrespect to one another.
 4. A method comprising: reducing interference ina cellular radio communications network by: identifying a plurality ofuser terminals exhibiting mutual interference with respect to oneanother; and adaptively adjusting at least one parameter of one or morecells of the cellular radio communications network by: modifying a cellboundary of at least one cell to reduce interference in at least one ofsaid plurality of user terminals; determining whether at least one ofsaid plurality of user terminals leave the cellular radio communicationsnetwork; and substantially restoring the adjusted at least one parameterto a non-adjusted value if at least one of said plurality of userterminals leaves the cellular radio communications network.
 5. Themethod of claim 4, wherein modifying the cell boundary redistributes acell load to reduce the interference.
 6. The method of claim 5, whereinthe interference comprises at least inter-cell interference received bytwo or more user terminals.
 7. The method of claim 4, wherein the atleast one parameter comprises a transmission parameter.
 8. The method ofclaim 6, wherein the transmission parameter is selected from the groupconsisting of a pilot power, a total transmission power, and a datechannel power.
 9. The method of claim 4, wherein said adjusting furthercomprises adjusting at least one parameter based at least in part on aperformance measurement.
 10. The method of claim 9, wherein theperformance measurement is included in a measurement report receivedfrom a user terminal.
 11. The method of claim 10, wherein theperformance measurement is a user terminal measurement selected from thegroup consisting of a pilot power, a ratio of pilot power tointerference for the an active set, and a ratio of pilot power tointerference for the neighboring set.
 12. A method comprising:identifying two or more cells of a cellular radio communications networkhaving an unbalanced load with respect to one another; and modifying acell boundary of a cellular radio communications network of at least oneof said two or more cells by adaptively adjusting at least one antennaparameter of one or more cells of the cellular radio communicationsnetwork to at least partially balance a load between the two or morecells, wherein said adaptively adjusting further comprises: determiningwhether at least one of said two or more cells leave the cellular radiocommunications network; and substantially restoring the modified cellboundary to a non-adjusted value if at least one of said two or morecells leave the cellular radio communications network.
 13. The method ofclaim 12, further comprising: adaptively adjusting a pilot power of oneor more cells to further modify a cell boundary.
 14. The method of claim13, wherein network capacity is increased due to a redistribution of acell load.
 15. A machine-readable medium having one or more executableinstructions stored thereon, which when executed perform a methodcomprising: reducing interference in a cellular radio communicationsnetwork by: identifying a plurality of user terminals exhibiting mutualinterference with respect to one another; and adaptively adjusting atleast one parameter of one or more cells of the cellular radiocommunications network to modify a cell boundary of at least one cell toreduce interference in at least one of said plurality of user terminals,wherein said adaptively adjusting further comprises: determining whetherat least one of said plurality of user terminals leave the cellularradio communications network; and substantially restoring the adjustedat least one parameter to a non-adjusted value if at least one of saidplurality of user terminals leaves the cellular radio communicationsnetwork.
 16. The machine-readable medium of claim 15, wherein modifyingthe cell boundary redistributes a cell load to reduce the interference.17. The machine-readable medium of claim 16, wherein the interference isinter-cell interference received by two or more user terminals.
 18. Themachine-readable medium of claim 16, wherein the at least one parameteris a transmission parameter.
 19. The machine-readable medium of claim18, wherein the transmission parameter is selected from the groupconsisting of a pilot power, a total transmission power, and a datachannel power.
 20. The machine-readable medium of claim 15, wherein theat least one parameter is adjusted adaptively to reduce interference inthe plurality of user terminals.
 21. The machine-readable medium ofclaim 20, wherein the at least one parameter is adjusted in accordancewith a performance measurement.
 22. The machine-readable medium of claim21, wherein the performance measurement is included in a measurementreport received from a user terminal.
 23. The machine-readable medium ofclaim 22, wherein the performance measurement is a user terminalmeasurement selected from the group consisting of a pilot power, a ratioof pilot power to interference for the an active set, and a ratio ofpilot power to interference for the neighboring set.